Solar collection facilities utilize solar concentrators and/or photovoltaic panels for harnessing solar energy. Solar concentrator assemblies (SCAs) utilizing parabolic trough collectors present large reflective surface areas (apertures) for tracking the sun and focusing the captured radiant energy on heat collection elements (HCEs) as a first step in a thermomechanical conversion process for generating electrical power. FIG. 1 illustrates a typical SCA 10 according to the prior art, the SCA 10 including a row of parabolic, cylindrically curved, or otherwise curved, troughs 20 for collecting radiant solar energy. The troughs 20 have reflective surfaces for reflecting and focusing the radiant energy on a heat collection tube 25. Each of the troughs 20 is supported by a corresponding trough frame 30, which may be constructed of tubes, bars, extrusions, and/or any other suitable structural members known in the art for supporting and maintaining the critical shape of each of the troughs 20 and the reflective surfaces thereon. Each of the trough frames 30 includes two torque plates 35, one on either side, for coupling to and supporting the trough frames 30 on supporting pylons 40. The torque plates 35, may, for example, be coupled to the supporting pylons 40 at bearings 45. Further, each of the supporting pylons 40 may support one side of each of two adjacent trough frames 30. A solar-trough solar power generation facility typically includes many SCAs, similar to the SCA 10 depicted in FIG. 1, arranged in rows to capture great amounts of solar radiant energy.
A typical arrangement for an SCA is to have a row of twelve troughs track the sun utilizing a single-axis center drive unit located at the center of the SCA with six troughs connected continuously on either side. Of course, an SCA may include any other suitable number of troughs. FIG. 2 shows the SCA 10 including a center drive unit (“center drive mechanism” or “torque drive mechanism”) 15 mounted on and supported by a central pylon 18, and six trough frames 20a, 20b, 20c, 20d, 20e, 20f in a row on one side of the center drive unit 15 and supported by supporting pylons 40a, 40b, 40c, 40d, 40e, 40f. The SCA 10 also includes six more trough frames in a row on the opposite side of the center drive unit 15, although only the innermost trough frame 20g on the opposite side is partially shown in FIG. 2. The center drive unit 15 drives a rotational movement of the twelve trough frames in unison, and also provides braking via various means. During daylight hours the SCA 10 operates as long as the wind speed does not exceed a certain threshold. Once the maximum operational wind speed is reached, then the troughs 20 are brought to a stowed position for protection (see FIG. 3). As illustrated in FIG. 3, the stowed position of the troughs 20 is defined by a downward facing orientation such that the curved, reflective surfaces are less exposed to the force of the wind. A downward facing angle α with respect to the ground may, in one embodiment, be approximately 30 degrees. Of course, another angle of orientation may be utilized for the stowed position of the troughs 20. To “lock down” the SCA 10 during high winds, a braking mechanism is applied by the center drive unit 15. During lock down, wind loading creates a twisting effect on each trough 20 and associated trough frame 30 that accumulates down the line of troughs from the outermost trough 20a toward the innermost trough 20f and the center drive unit 15. Governing design loads for the trough frames are based on the maximum accumulated twisting (torque) experienced by the innermost frame 20f. 
Single, torque brakes (locking solenoids) integral with the center drive mechanism have been used for braking a solar concentrator assembly (SCA), such as for the Nevada Solar One installation. Alternatively, hydraulic ram positioning has been used for SCA braking, such as on the SEG plants in the California Mojave Desert.
Problems develop because wind blowing against the troughs 20 creates twisting of the trough frames 30. Because the SCA 10 includes a number of troughs 20 connected to each other in a row, the outermost trough 20a will experience a first torsional load due to wind forces. This first torsional load is transferred to the second outermost trough 20b because it is connected to the outermost trough 20a through the trough frames 30. Additionally, wind forces apply a second torsional load to the second outermost trough 20b, approximately equal to the first torsional load. Therefore, the second outermost trough 20b is subjected to a combined torsional load approximately twice as great as that applied to the outermost trough 20a. Similarly, along the row of troughs of the SCA 10, each adjacent trough and associated trough frame is subjected to a greater torsional load than an outer adjacent trough and trough frame. Finally, the torsional loads accumulate to critical levels at the innermost troughs 20f, 20g on either side of the center drive unit 15. For example, in the SCA 10 having twelve troughs 20, six on either side of the center drive unit 15, the innermost trough frames 20f, 20g are subjected to a torsional load that is approximately six times greater than the first torsional load on the outermost trough 20a. 
Traditionally, the center drive unit 15 has been utilized both to rotate and brake the twelve trough collectors. The torsional loads are critical at survival wind speeds when the center drive unit 15 serves only as a brake. Consequently, all of the trough frames 30 and connected hardware are sized to withstand the maximum torsional load, which is experienced only by the two innermost trough frames 20f, 20g. That is, utilizing the traditional system of braking, either each of the trough frames 30 of the SCA 10 must be designed to withstand the maximum torsional load, which is only applied at the trough frames 30 of the innermost troughs 20f, 20g, or the trough frames 30 must be designed having varying degrees of strength to withstand the varying torsional loads applied to each of the trough frames 30 along the row of troughs. Each of these two possibilities leads to increased cost. Furthermore, requiring the sum of the torques accumulated along the row of trough frames 30 to be borne by the center drive unit 15, as seen in the prior art, necessitates the use of a sturdier, more expensive, and possibly custom-built, center drive unit 15.